Vitamin B12 is a vitamin that plays a role in mammalian growth, hematopoiesis, production of epithelial cells and maintenance of the nervous system. It is quite water-soluble and thus could be expected to be easily available to human subjects. However, the absorption from the gut of normal dietary amounts of vitamin B12 is believed to be dependent on gastric Intrinsic Factor (GIF), and the loss of Intrinsic Factor leads to vitamin B12 deficiency. The loss of ability to absorb vitamin B12 (B12) is the most common cause of adult B12 deficiency. Such a loss may, for example, be due to pernicious anemia (with loss of Intrinsic Factor) or to a number of other conditions that decrease production of gastric acid, which also plays a part in absorption of B12 from foods. Deficiency is most significantly linked to inadequate absorption rather than low consumption, as those who consume high amounts of vitamin B12 may still experience deficiency as evidenced by a low blood concentration. Vitamin B12 deficiency results in various undesirable conditions such as fatigue, depression, poor memory, etc. [Source: Wikipedia]. Other causes of vitamin B12 deficiency include atrophic gastritis (a thinning of the stomach lining), surgery in which part of the stomach and/or small intestine is removed, conditions affecting the small intestine (such as Crohn's disease, celiac disease, bacterial growth, or a parasite), excessive alcohol consumption, autoimmune disorders (such as Graves' disease or systemic lupus erythematosus) and drug abuse.
Pharmaceutical compositions containing vitamin B12 according to the preamble are known in the art, for example from U.S. Pat. No. 5,801,161 to Merkus, which discloses an intranasal spray. Such a pharmaceutical composition is brightly red, with as the concomitant disadvantage that any fluid of the pharmaceutical composition running from the nose will give the appearance of a bloody nose. Further prior art includes i) Nascobal, a nasal solution of cyanocobalamin available in the USA, and ii) (Br. J. Clin. Pharmacol, 1998, January, 45(1): 83-86 to Asselt et al, showing that hydroxocobalamin nasal sprays are effective in treating vitamin B12 deficiency in elderly adults.